It seems as if you're describing a common symptom of ordinary sleep paralysis, like you mentioned.
I don't know if your looking for a 'supernatural' explanation, or if a biological one would do.
If the latter is the case (or maybe both?), perhaps a brief Wikipedia-overview could help: http://en.wikipedia.org/wiki/Sleep_paralysis#Symptoms

If the latter is the case (or maybe both?), perhaps a brief Wikipedia-overview could help: http://en.wikipedia.org/wiki/Sleep_paralysis#Symptoms